French duo Tancrède Melet and Julien Millot are masters of highlining. Untethered and thousands of metres above sea level, they BASE jump into the void, synthesizing a new sport they call BASE Lining.

Bernhard Witz and co reach the top of Angel Falls in Venezuela, the highest waterfall in the world. But illness threatens their plan to traverse a highline suspended 2,625 feet above the jungle.

Using sophisticated technology to hunt fearsome storms that create monster-sized swells, veteran surfers Ross Clarke-Jones and Tom Carroll set off for the unridden waves of Pedra Branca.

The Wrangell Mountains in Alaska may be out of bounds for helicopters, but they won’t stop legendary freeride snowboarder Jeremy Jones. He ventures by foot to find the fastest route down.

A freak swell that creates a towering wave in Tahiti and a rare rolling cloud that looms dangerously in the skies above Australia are irresistible lures for athletes to confront these natural wonders.

Most people's nightmares are a dream come true for Jeb Corliss, a world-class BASE jumper whose surreal flights nearly end when he gets too close for comfort to South Africa's Table Top Mountain.

When Italian model and skydiver Roberta Mancino meets BASE jumper Jeb Corliss, their lives soar to new heights. Two people sharing a long-held dream of flying become a love story for the ages.

Tapping into the "flow," a meditative state in which an athlete becomes one with his surroundings, Ben Brown battles life-threatening weather to lead a kayaking expedition across New Zealand.

Cycling for 5,000km (3,100mi) and negotiating 30,000m (98,000ft) of climbs and descents, Gerhard Gulewicz subjects his body to unimaginable physical exertion to ride from California to Maryland.

Venturing to ascend the impressive Cerro Autana, climbers Leo Houlding, Jason Pickles and Sean Leary trek deep into the Amazon to discover why this summit has never been reached from the east.

Dean's Blue Hole in the Bahamas is the world's deepest saltwater blue hole. It's also the backdrop for William Trubridge's record attempt to finless dive 300 feet below the surface in just one breath.

At least 16 expeditions have tried to summit the 8,000m peak called Gasherbrum II during the Pakistani winter. They all failed. Determined to beat the stats, Cory Richards documents his team's ascent.

In their quest to be the first to summit Ulvetanna Peak in Antarctica, Leo Houlding, Jason Pickles and Sean Leary will need good weather and all their experience to best a frozen 2,931m challenge.

Dropping through towering shafts, Chris Jewell's team descends a mile into the earth to set the record for deepest cave dive in the Western Hemisphere at Mexico's Huautla Cave System.

Darren Berrecloth leads a group of mountain bikers through the hostile terrain of Nepal's Upper Mustang and China's Gobi Desert, carrying their bikes to reach the world's most breathtaking descents.

Ice climber Harald Berger waits for one of Austria's most stunning waterfalls to freeze over. The Supervisor is a thousand-foot cascade of ice that he’s determined to conquer in a free solo ascent.

As a wingsuit pilot and BASE-jumper, Cédric Dumont knows about fear. Whether flying just above ground in Switzerland or jumping from a waterfall in Peru, he fights a mental battle with fear.

Behind the scenes, the filmmakers that capture the thrilling action sports feats of Ultimate Rush blend art, craft and technical skill with a physical courage that rivals the athletes themselves.